This invention relates to improvements in line protectors of the type that are located between central office switching equipment and inside switching related equipment. These protectors serve to protect the inside equipment from damage as a result of overvoltage and overcurrent conditions on the outside lines. Examples of such protectors are shown in U.S. Pat. No. 3,743,888 issued July 3, 1973; U.S. Pat. No. 3,573,695 issued Apr. 6, 1971; U.S. Pat. No. 3,587,021 issued June 22, 1971; U.S. Pat. No. 3,255,330 issued June 7, 1966 and U.S. Pat. No. 3,849,750 issued Nov. 19, 1974. More particularly, the present invention is an improvement in the line protector of the type shown in the aforesaid U.S. Pat. No. 3,849,750. Such line protectors are commonly referred to in the art as central office protectors.
Many protectors of the foregoing type employ a heat coil responsive to over current conditions in the line to cause a fusible solder element to melt and thereby allow a spring to bring a pair of contacts together and form a direct metallic circuit from the protected line to ground. Because the heat coil is directly in the line circuit there sometimes tends to be noise on the line during normal operating conditions due to one or more surface-to-surface contacts of components in the line circuit within the protector. These surface-to-surface components tend to become contaminated in some cases despite efforts to shield or enclose fully the interior mechanism of the protector. The collection of dust and the presence of corrosive elements in the atmosphere all contribute to the creation of noisy contacts where the interfaced terminations are provided by simple abutting contact even if the contacts are under the influence of spring pressure.